Moderate atmospheric temperature and pressure make surface liquid water possible ‣ ‣ ‣ What is Venus like today? Venus has an extremely thick CO2 atmosphere Hottest planetary surface in the solar system How did Venus get so hot? Thick CO2 atmosphere leads to a ‣ ‣ ‣ ‣ huge greenhouse effect Why did Earth’s atmosphere end up so different? Temperatures just right for oceans of water Oceans keep most CO2 out of atmosphere ‣ ‣ ‣ ‣ What are jovian planets like? Thick hydrogen, helium atmospheres Layered interiors with very high pressure and cores made of rock, metals, and hydrogen compounds Very high pres ‣ ‣ ‣ - sure in Jupiter and Saturn can produce metallic hydrogen All have strong storms and winds What kinds of moons orbit jovian planets? Moons of many sizes Many major moons show ‣ ‣ ‣ ‣ signs of geological activity Tidal heating drives activity Titan is the only moon with a thick atmosphere ‣ ‣ ‣ What are Saturn’s rings like? Made up of countless individual ice particles Extremely thin with many gaps How do other jovian ring systems compare to Saturn’s? Much fainter ring ‣ ‣ ‣ ‣ systems with smaller, darker, less numerous particles Why do the jovian planets have rings? Ring particles are probably debris from moons ‣ ‣ What are asteroids like? Rocky leftovers from the era of planet formation Generally irregular in shape Some are “rubble piles” The majority are found in the asteroid belt, between the ‣ ‣ ‣ ‣ orbits of Mars and Jupiter What are comets like? Comets are like dirty snowballs Most are far from Sun and do not have tails Tails grow when comet nears Sun and the nucleus heats ‣ ‣ ‣ ‣ up Comets come from Kuiper Belt and Oort cloud ‣ What are meteoroids, meteors, & meteorites? Meteoroid - small debris in space Meteor - bright streak in the air cause by falling debris Meteorite - space rock on the ground Most mete ‣ ‣ ‣ ‣ - ors are comet debris, but meteorites come from asteroid debris Did a meteorite impact kill the dinosaurs? An iridium-rich sediment layer and an impact crater on the Mexican coast show ‣ ‣ that a large impact occurred at the time the dinosaurs died out, 65 million years ago The Sun The Sun’s size, composition, and temperature The Sun generates energy through hydrogen fusion in the core That energy first moves through the radiative zone of the Sun as ‣ ‣ ‣ light Then it warms the gas in the convective zone of the Sun and that hot gas bubbles up to the photosphere, producing granules Thermal Radiation Hot objects naturally give off light ‣ ‣ ‣ ‣ The color of that light depends on the temperature of the object The Sun and other stars light comes from this thermal radiation Neutrinos The fusion in the Sun’s core produces neutrinos ‣ ‣ ‣ Neutrinos are VERY hard to detect, but we have telescopes that can detect a few Through neutrino observations, we can take a direct image of the core of the Sun! ‣ ‣ The Sun’s Atmosphere The photosphere is the “surface” of the Sun, which is about 5800 K The chromosphere is the thin layer just above the photosphere The corona is the upper atmos ‣ ‣ ‣ - phere of the Sun, extremely thin but VERY hot as well Sunspots Sunspots are dark spots on the photosphere of the Sun They are dark because they are cooler than the rest of the photo ‣
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